The invention relates to a backup breathing gas supply for high altitude flying where the main breathing supply is provided by a pressure swing adsorption system.
The use of pressure swing adsorption systems or concentrators to derive an oxygen enriched product gas through the pressure swing adsorption technique is well known. This technique involves the use of two or more molecular sieve beds which trap certain components of air while letting selected other components pass through the system as enriched product gas. The output of such systems may be oxygen which is used as a breathing gas supply for a pilot engaged in high altitude flying.
The pressure swing adsorption system itself is designed to eliminate the need for providing a bottled oxygen breathing gas supply on an aircraft. However, it is desirable to have a backup breathing gas supply in the event of a failure in the concentrator system. The backup supply is used during brief periods of interruption of concentrator output caused by one or more of the following conditions: (1) loss of bleed air due to aircraft engine flame out; (2) loss of electrical power and resulting concentrator pressure cycling due to an open circuit breaker; or (3) failure of concentrator cycling due to a stopped rotary valve.
Although a concentrator derived breathing gas supply is intended to replace bottled gas and/or stored liquid oxygen for normal operation, bottled gas is often used as the backup breathing gas supply for aircraft. This is undesirable since it requires the storage and handling of the bottled oxygen which is costly, hazardous, and unavailable in remote areas.